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Toxic Equivalency Factor
Toxic equivalency factor (TEF) expresses the toxicity of dioxins, furans and PCBs in terms of the most toxic form of dioxin, 2,3,7,8-TCDD.Van den Berg M, Birnbaum LS, Denison M, De Vito M, Farland W, Feeley F, Fiedler H, Hakansson H, Hanberg A, Haws L, Rose M, Safe S, Schrenk D, Tohyama C, Tritscher A, Tuomisto J, Tysklind M, Walker N, Peterson RE. 2006. The 2005 World Health Organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-like compounds, Toxicol. Sci. 93:223–241, doi:10.1093/toxsci/kfl055. The toxicity of the individual congeners may vary by orders of magnitude. With the TEFs, the toxicity of a mixture of dioxins and dioxin-like compounds can be expressed in a single number – the toxic equivalency (TEQ). It is a single figure resulting from the product of the concentration and individual TEF values of each congener. The TEF/TEQ concept has been developed to facilitate risk assessment and regulatory control. While the init ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toxicity
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (biology), cell (cytotoxicity) or an organ such as the liver (hepatotoxicity). Sometimes the word is more or less synonymous with poison#Poisoning, poisoning in everyday usage. A central concept of toxicology is that the effects of a toxicant are Dose (biochemistry), dose-dependent; even water can lead to water intoxication when taken in too high a dose, whereas for even a very toxic substance such as snake venom there is a dose below which there is no detectable toxic effect. Toxicity is species-specific, making cross-species analysis problematic. Newer paradigms and metrics are evolving to bypass animal testing, while maintaining the concept of toxicity endpoints. Etymology In Ancient G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biomagnify
Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance, e.g a pesticide, in the tissues of organisms at successively higher levels in a food chain. This increase can occur as a result of: * Persistence – where the substance cannot be broken down by environmental processes. * Food chain energetics – where the substance's concentration increases progressively as it moves up a food chain. * Low or non-existent rate of internal degradation or excretion of the substance – mainly due to water-insolubility. Biological magnification often refers to the process whereby substances such as pesticides or heavy metals work their way into lakes, rivers and the ocean, and then move up the food chain in progressively greater concentrations as they are incorporated into the diet of aquatic organisms such as zooplankton, which in turn are eaten perhaps by fish, which then may be eaten by bigger fish, large birds, anim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concentration Indicators
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', and ''volume concentration''. The concentration can refer to any kind of chemical mixture, but most frequently refers to solutes and solvents in solutions. The molar (amount) concentration has variants, such as normal concentration and osmotic concentration. Dilution is reduction of concentration, e.g. by adding solvent to a solution. The verb to concentrate means to increase concentration, the opposite of dilute. Etymology ''Concentration-'', ''concentratio'', action or an act of coming together at a single place, bringing to a common center, was used in post-classical Latin in 1550 or earlier, similar terms attested in Italian (1589), Spanish (1589), English (1606), French (1632). Qualitative description Often in informal, non-techn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dioxins And Dioxin-like Compounds
Dioxins and dioxin-like compounds (DLCs) are a group of chemical compounds that are persistent organic pollutants (POPs) in the environmental pollutant, environment. They are mostly by-products of burning or various industrial processes or, in the case of dioxin-like polychlorinated biphenyl, PCBs and polybrominated biphenyl, PBBs, unwanted minor components of intentionally produced mixtures. Some of them are highly toxic, but the toxicity among them varies 30,000-fold. They are grouped together because their mechanism of action is the same. They activate the aryl hydrocarbon receptor (AH receptor), albeit with very different binding affinities, leading to high differences in toxicity and other effects. They include: * Polychlorinated dibenzodioxins, Polychlorinated dibenzo''-p-''dioxins (PCDDs), or simply dioxins. PCDDs are derivatives of dibenzodioxin, dibenzo''-p-''dioxin. There are 75 PCDD congener (chemistry), congeners, differing in the number and location of chlorine atoms, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychlorinated Naphthalene
Polychlorinated naphthalene (PCN) are the products obtained upon treatment of naphthalene with chlorine. The generic chemical formula is Carbon, C10Hydrogen, H8−(m+n)Chlorine, Cl(m+n). Commercial PCNs are mixtures of up to 75 components and byproducts.van de Plassche, E.; Schwegler, A. (2002)''Polychlorinated naphthalenes, Preliminary Risk Profile'' Ministry of VROM/DGM, Netherlands The material is an oil or a waxy solid, depending on the degree of chlorination. PCNs were once used in insulating coatings for electrical wires, as well as other applications, but their use has been largely phased out. Chemical structure of PCN congeners There are 75 different PCN congener (chemistry), congeners. Production PCNs started to be produced for high-volume uses around 1910 in both Europe and the United States.Chlorinate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clean Water Act
The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the primary responsibilities of the states in addressing pollution and providing assistance to states to do so, including funding for publicly owned treatment works for the improvement of wastewater treatment; and maintaining the integrity of wetlands.Jim Hanlon, Mike Cook, Mike Quigley, Bob Wayland"Water Quality: A Half Century of Progress."EPA Alumni Association. March 2016. The Clean Water Act was one of the United States' first and most influential modern environmental laws. Its laws and regulations are primarily administered by the U.S. Environmental Protection Agency (EPA) in coordination with state governments, though some of its provisions, such as those involving filling or dredging, are administered by the U.S. Army Corps of Engineers. Its impl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superfund
Superfund is a United States federal environmental remediation program established by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). The program is administered by the United States Environmental Protection Agency, Environmental Protection Agency (EPA) and is designed to pay for investigating and cleaning up sites contaminated with hazardous substances. Sites managed under this program are referred to as Superfund sites. Of the tens of thousands of sites selected for possible action under the Superfund program, 1178 (as of 2024) remain on the National Priorities List (NPL)The EPA and state agencies use the ''Hazard Ranking System (HRS)'' to calculate a site score (ranging from 0 to 100) based on the actual or potential release of hazardous substances from a site. A score of 28.5 places a site on the National Priorities List, eligible for cleanup under the Superfund program. that makes them eligible for cleanup under the Superfund prog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Risk Assessment
Risk assessment is a process for identifying hazards, potential (future) events which may negatively impact on individuals, assets, and/or the environment because of those hazards, their likelihood and consequences, and actions which can mitigate these effects. The output from such a process may also be called a risk assessment. Hazard analysis forms the first stage of a risk assessment process. Judgments "on the tolerability of the risk on the basis of a risk analysis" (i.e. risk evaluation) also form part of the process. The results of a risk assessment process may be expressed in a quantitative or qualitative fashion. Risk assessment forms a key part of a broader risk management strategy to help reduce any potential risk-related consequences. Categories Individual risk assessment Risk assessments can be undertaken in individual cases, including in patient and physician interactions. In the narrow sense chemical risk assessment is the assessment of a health risk in response ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chronic Toxicity
Chronic toxicity, the development of adverse effects as a result of long term exposure to a contaminant or other stressor, is an important aspect of aquatic toxicology. Adverse effects associated with chronic toxicity can be directly lethal but are more commonly sublethal, including changes in growth, reproduction, or behavior. Chronic toxicity is in contrast to acute toxicity, which occurs over a shorter period of time to higher concentrations. Various toxicity tests can be performed to assess the chronic toxicity of different contaminants, and usually last at least 10% of an organism's lifespan. Results of aquatic chronic toxicity tests can be used to determine water quality guidelines and regulations for protection of aquatic organisms. Definition Chronic toxicity is the development of adverse effects as the result of long term exposure to a toxicant or other stressor. It can manifest as direct lethality but more commonly refers to sublethal endpoints such as decreased growth, r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acute Toxicity
Acute toxicity describes the adverse effects of a substance that result either from a single exposure or from multiple exposures in a short period of time (usually less than 24 hours). To be described as ''acute'' toxicity, the adverse effects should occur within 14 days of the administration of the substance. Acute toxicity is distinguished from chronic toxicity, which describes the adverse health effects from repeated exposures, often at lower levels, to a substance over a longer time period (months or years). It is widely considered unethical to use humans as test subjects for acute (or chronic) toxicity research. However, some information can be gained from investigating accidental human exposures (e.g., factory accidents). Otherwise, most acute toxicity data comes from animal testing or, more recently, ''in vitro'' testing methods and inference Inferences are steps in logical reasoning, moving from premises to logical consequences; etymologically, the word ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In Vitro
''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology and its subdisciplines are traditionally done in labware such as test tubes, flasks, Petri dishes, and microtiter plates. Studies conducted using components of an organism that have been isolated from their usual biological surroundings permit a more detailed or more convenient analysis than can be done with whole organisms; however, results obtained from ''in vitro'' experiments may not fully or accurately predict the effects on a whole organism. In contrast to ''in vitro'' experiments, ''in vivo'' studies are those conducted in living organisms, including humans, known as clinical trials, and whole plants. Definition ''In vitro'' (Latin language, Latin for "in glass"; often not italicized in English usage) studies are conducted ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In Vivo
Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and plants, as opposed to a tissue extract or dead organism. Examples of investigations ''in vivo'' include: the pathogenesis of disease by comparing the effects of bacterial infection with the effects of purified bacterial toxins; the development of non-antibiotics, antiviral drugs, and new drugs generally; and new surgical procedures. Consequently, animal testing and clinical trials are major elements of ''in vivo'' research. ''In vivo'' testing is often employed over ''in vitro'' because it is better suited for observing the overall effects of an experiment on a living subject. In drug discovery, for example, verification of efficacy ''in vivo'' is crucial, because ''in vitro'' assays can sometimes yield misleading results with drug c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
